The present invention relates to a two-way optical communication as well as to a transmitting and receiving optoelectronic device for a digital optical subscriber transmission system and, more particularly, to a filter separation type of transmitting and receiving optoelectronic device.
It is known that transmitting and receiving optoelectronic devices are employed for two-way optical communication, particularly, transmission and reception in digital optical subscriber transmission systems. As shown in FIG. 4 (schematic diagram), such a transmitting and receiving optoelectronic device includes, for example, a light transmitter having an LD (laser diode) element 2 and a transmission-side condenser 17 which cooperate to emit transmission light 5 of wavelength .lambda..sub.1 ; an optical fiber 19 for guiding the transmission light 5 emitted from the light transmitter; a light receiver having a PD (photodiode) element 8 which is sensitive to reception light 12 of wavelength .lambda..sub.2 passing through the optical fiber 19 (by propagation), a wave-separating filter 9 which reflects the transmission light 5 of wavelength .lambda..sub.1 and transmits the reception light 12 of wavelength .lambda..sub.2, and a reception-side condenser 18; a wave-separating filter 16 which transmits the transmission light 5 of wavelength .lambda..sub.1 and reflects the reception light 12 of wavelength .lambda..sub.2 ; and a wave-separating filter support 25 for supporting the wave-separating filter 16. In such a transmitting and receiving optoelectronic device, the PD element 8 is disposed at a position approximately perpendicular to the transmission light 5, while the wave-separating filter 16 is disposed at an angle of 45.degree. with respect to the transmission light 5. In the transmitting and receiving optoelectronic device, a light passage hole 25A for guiding the transmission light 5 emitted from the light transmitter to the wave-separating filter 16 is formed in the wave-separating filter support 25. The internal wall surface of the light passage hole 25A in the wave-separating filter support 25 is formed approximately in parallel with the optical axis of the transmission light 5.
Other types of transmitting and receiving optoelectronic devices are known. One example is arranged to perform optical communication by using a signal wavelength. The transmitting and receiving optoelectronic device disclosed in Japanese Patent Laid-Open No. 237408/1987 adopts two lens systems as its focusing optical system.